Talk to anyone who lived in New York City in the 1970s, and they will probably highlight the city’s widespread crime. Times Square wasn’t yet Disney-fied and Brooklyn hadn’t been taken over by hipsters. Most people agreed that New York was a dangerous place. But then something happened: murders, and violent crime in general, began to drop. And that trend wasn’t unique to New York: It happened in many places across America. So who do we have to thank for the crime decline? To find out, we talk with NYU sociology professor Patrick Sharkey about his book “Uneasy Peace: The Great Crime Decline, Renewal of City Life, and the Next War on Violence.”

Unless we’re relaxing on it at the beach, or kicking it out of our shoes, we probably don’t think too much about sand. But that doesn’t mean it isn’t important. Sand is a vital ingredient in concrete. And glass. And asphalt. It makes our modern, urban life possible. And our hunger for it is causing more and more trouble.

Vince Beiser, author of “The World in a Grain: The Story of Sand and How It Transformed Civilization,” explains why sand matters, and how the quest to extract more of it is shaping the world.

When you think of evolution, you probably imagine a slow process, one that happens in some verdant jungle or plain. For example: Homo Sapiens gradually evolving over millions of years on the savannah. Or the finches of the Galapagos adapting to their unique environment. But Menno Schilthuizen, a biologist and author of “Darwin Comes to Town: How the Urban Jungle Drives Evolution,” says that evolution can hapen a lot faster, and a lot closer to us, than we might think. And humans, along with the cities we build, drive a lot of it.

What were pregnancy tests like in the 1940s? Well, they involved cutting up rabbits. How the science of hormones changed pregnancy, diabetes, and so much more.

If you want to track down the first telecommunications hack, you have to go back in time. All the way to the 1830s.

America is aging. And so are the people who control our money. How that’s going to upend our economy.

Doctor Randi Hutter Epstein likes to compare human hormones to the internet. And if you think about it, it makes sense. The brain sends messages to the testes in the same way that someone in Paris can send an email to someone in Tokyo. There’s no apparent infrastructure that connects the senders and receivers. Just a message floating out there, knowing what its target is. But it took a very long time before we had this kind of basic understanding of hormones. And, even today, most people doesn’t understand the power of these chemicals. We talk to Epstein, author of, “Aroused: The History of Hormones and How They Control Just About Everything,” about how we came to understand the endocrine system.

What was the world’s first telecommunications hack? Some sort of electronic banking theft in the 80s? Perhaps it was the “phone breaks” of the 1960s, who used tricks to make calls for free? Or the scientific hooligans who hacked Marconi’s wireless? Well, according to Tom Standage, Deputy Editor of The Economist, you have to go back even further than that. To 19th-century France, and a new technology called the mechanical telegraph.

The United States is about to face a “silver tsunami;” a retirement crisis; a health care dilemma. At least, that’s what it seems like, if you read articles about America’s aging population of baby boomers. And the increased number of older Americans *is *going to transform the country. The US Census bureau says that “older adults will outnumber chil­dren for the first time in U.S. history” in just a few decades. And they will transform the economy to fit their needs and wants. This presents both challenges and opportunities, according to Joseph Coughlin, author of, “The Longevity Economy: Unlocking the World’s Fastest-Growing, Most Misunderstood Market.”

Are college kids becoming more fragile? Social psychologist Jonathan Haidt says yes. And he explains why.

How a Coney Island sideshow helped save infants lives.

Termites! They may be super gross… but we can also learn a lot from them.

For the last few years, free speech has been hotly debated on college campuses around the country. There have been protests over controversial speakers. And confrontations around the cultural sensitivity of halloween costumes. Jonathan Haidt, a social psychologist at NYU and co-author of The Coddling of the American Mind: How Good Intentions and Bad Ideas Are Setting Up a Generation for Failure, sees deeper issues at play. Issues that he thinks are going to impact an entire generation.

In the early 20th century, a premature baby was considered as good as dead. But Dr. Martin Couney — who wasn’t actually a doctor — made it his mission to save these babies by putting them neonatal incubators. And Couney had a flair for the dramatic. He would put incubated babies on display at Coney Island, and at World’s Fairs, where people could see them — IF they paid a quarter. We talk to Dawn Raffel about her new biography, “The Strange Case of Dr. Couney: How a Mysterious European Showman Saved Thousands of American Babies.”